INSIVUMEH reported that effusive activity at Fuego decreased as of 16 September; the lava flow that had descended the Ceniza drainage (SSW) was no longer active. There were 6-16 explosions per hour recorded during 16-22 September, generating ash plumes as high as 1.1 km above the crater rim that generally drifted 7-20 km in multiple directions. Shock waves rattled buildings within a 20-km radius. Sometimes incandescent material ejected 100-300 m high caused avalanches of blocks in the Ceniza, Seca (W), Trinidad (S), Taniluyá (SW), Las Lajas, and Honda drainages; avalanches sometimes reached vegetated areas. Ashfall was reported daily in several areas downwind including Morelia (9 km SW), Panimaché I and II (8 km SW), Finca Palo Verde, Santa Sofía (12 km SW), San Pedro Yepocapa (8 km NW), and Sangre de Cristo (8 km WSW). During 18-19 September lahars descended the Ceniza, Las Lajas, and Honda drainages, carrying tree branches, trunks, and blocks as large as 1.5 m in diameter. Additionally, lava flows traveled 200-350 m down the Seca and Ceniza drainages.

Geological Summary. Volcán Fuego, one of Central America's most active volcanoes, is also one of three large stratovolcanoes overlooking Guatemala's former capital, Antigua. The scarp of an older edifice, Meseta, lies between Fuego and Acatenango to the north. Construction of Meseta dates back to about 230,000 years and continued until the late Pleistocene or early Holocene. Collapse of Meseta may have produced the massive Escuintla debris-avalanche deposit, which extends about 50 km onto the Pacific coastal plain. Growth of the modern Fuego volcano followed, continuing the southward migration of volcanism that began at the mostly andesitic Acatenango. Eruptions at Fuego have become more mafic with time, and most historical activity has produced basaltic rocks. Frequent vigorous historical eruptions have been recorded since the onset of the Spanish era in 1524, and have produced major ashfalls, along with occasional pyroclastic flows and lava flows.

Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH)